Revised Fuel Economy Ratings Closer to Actual MPG

by Don Elliott on June 9, 2011

Did you know that, in the 2008 model year, the government revised the way miles per gallon (MPG) is calculated? It had been over 40 years since the calculation criteria were first established. If your car is older than the 2008 model year, there is a good chance you have not been getting the MPG rating posted on the new car window sticker. Fortunately, it is probably not all your aging vehicle’s fault.

The Environmental Protection Agency (EPA) is responsible for maintaining accurate fuel economy ratings for new and used cars and light-duty trucks. The Energy Independence and Security Act of 2007 mandated that testing procedures be updated to reflect more current vehicles and driving situations. 

More modern vehicles accelerate much more quickly than cars from four decades ago. Therefore, driving habits are more aggressive. The old ratings assumed 60 miles per hour as an average highway driving speed. Current tests include highway average speeds approaching 80 miles per hour. Current testing includes the use of more accessories like air conditioning, which was not part of the old standard. The new standards have also added 20 degree cold starts as part of the tests. Finally, the new measurements take into account different fuels including electricity, ethanol, liquid natural gas and hybrids of those fuels.

Current testing is performed at the National Vehicle and Fuel Emissions Laboratory in Ann Arbor, Michigan. Fuel economy ratings are reported to the Department of Energy (DOE) and summarized in their Fuel Economy Guide. Comparisons of the fuel economy ratings on 2007 model year cars and older cars with the new fuel economy standards are available on the fuel economy calculation website.

How are used car values impacted by changes in the fuel economy standards? 2008 model year vehicles and newer vehicles reflect lower miles per gallon numbers than 2007 model year vehicles and older. For example, an owner of a 2007 Toyota Prius expected to get an overall average of 55 MPG. If he were to shop for the same vehicle under the new standards, it would carry an overall rating of 46 MPG. It would appear that the fuel economy of the Prius dropped by 19%. In reality the Prius fuel economy performance didn’t change, but the government rating changed.

Actual fuel economy will vary from car to car because of different driving habits, traffic patterns, and other influences. However, buyers of 2008 model year vehicles and newer vehicles will experience fuel economy ratings that are much closer to their actual driving experience.

If this information on fuel economy ratings was helpful to you, send us a comment.

Google+ Comments

Previous post:

Next post: